Objective. Te evalúate the efficacy and safety of post-surgery analgesia with intravenous paracetamol (P-iv). Patient and Methods. Prospective, multicentre-observational study in patients who had surgery associated to mild or modérate postoperative pain (POP) that received 4 doses of P-iv 1 g /4-6h, alone or associated with other analgesics. The degree of pain by the visual analogue scale, effect on the activity, undesirable effects and patient satisfaction were recorded. Period of study: 24 hrs post-surgery. Statistics. Parametric or non-parametric, or a model of regression analysis. Results. 725 patient enrolled, 56% with mild POP and 43,3% modérate POP. EVA decreased significantly through the successive evaluations (p<0,001), but remained below 30. 46,3% received only P-iv as analgesic. Metamizol was the most frequently associated analgesic, followed by opiates. Higher levéis of EVA were correlated with: administration of associated analgesics, more interference with the activity, more nauseas and vomiting and smaller degree of satisfaction (p<0.05). The type of surgery was correlated with greater valúes of EVA. No undesirable effects caused by P-iv were observed. Conclusión. P-iv to 1 g/4-6 h is effective during the 24 first hours post-surgery that produces mild to modérate POP with few undesirable effects, and anaesthesia practice combines frequently P-iv with other analgesics, being the most frequent metamizol followed by opiates.